The present invention relates to a method for stuffer box crimping a multifilament yarn, as well as an apparatus for carrying out the method.
In the production of melt spun crimped yarns, it is known to compress the multifilament yarns to a yarn plug in a stuffer box chamber for purposes of crimping, so that the filaments of the yarn collect in loops and coils on the surface of the yarn plug and are compacted therein. In this process, a feed nozzle pneumatically advances the multifilament yarn into the stuffer box chamber. To this end, the feed nozzle comprises a yarn channel, into which a plurality of fluid feed channels terminate, through which a conveying fluid enters the yarn channel under an overpressure. The conveying fluid which is preferably heated thus causes the multifilament yarn to enter the yarn channel and advance therein.
A method and an apparatus of this type are disclosed, for example, in DE 44 35 923 A1.
In the known method and apparatus, the feed nozzle comprises guide means in a central supply channel for the conveying fluid, so as to obtain in an annular channel a preferred direction of flow of the conveying fluid. The annular channel supplies a plurality of fluid feed channels that connect the annular channel to the yarn channel. The oriented flow thus causes inside the yarn channel a twisting action to develop, which leads to a twisting of the yarn. To influence the twisting action on the yarn, it is proposed to adjust the guide means, so as to orient the flow in the annular channel to a greater or lesser extent. Depending on the yarn type, different requirements are to be met. On the one hand, a twist is desired for increasing a reliable advance, in particular upon the entry of the yarn. On the other hand, excessive twisting of the yarn may interfere with achieving a high crimp. In this respect, it is desirable to adjust the twisting action at the feed nozzle as precisely as possible. However, the known system is suited only to a limited extent for precisely adjusting and varying the twisting action on a multifilament yarn in a wider range.
In particular, it is necessary that such texturing nozzles be suited for reliably guiding both multifilament yarns consisting of a plurality of yarn bundles, for example, for the production of three-color yarns, and multifilament yarns consisting of one filament bundle, for example, for the production of single-color yarns, and for advancing them into an adjacent stuffer box chamber. In this process, quite different requirements are to be met by a twisting action of the feed nozzle, which the known solutions, however, accomplish only inadequately.
It is therefore an object of the invention to provide a method and an apparatus of the initially described type for stuffer box crimping a multifilament yarn, which permit adjusting as precisely as possible in a widest possible range a twist impartation that is caused by a conveying fluid in the yarn channel.
A further object of the invention is to provide a method and an apparatus for stuffer box crimping multifilament yarns with a high flexibility and applicability.